Kim et al. (2009) studied factors influencing intention to use mobile payment, using the final TAM together with external variables. Moreover, they also introduced moderating effects by comparing early adopter and late adopters. They found that mobile payment knowledge, mobility and reachability were important determinants to perceived ease of use for early adopters, whereas innovativeness and reachability were the main important determinants to perceived ease of use for late adopters. Furthermore, compatibility and convenience were also main determinants to perceived usefulness for late adopters. Perceived ease of use and perceived usefulness both had significantly positive relationships with intention to use, but the relationship between perceived usefulness and intention to use mobile payment was stronger for early adopters, whereas the relationship between perceived ease of use and intention to use was stronger for late adopters (Kim et al. 2009)